though i haven't read through the forum link posted above, i would say do it. i have acquired really nice things this way! and sorry, i don't consider it theft, i consider it reclamation. unfortunately not every one has this vision, including the police, so use your best judgement. do it in broad daylight, wear a union suit, put an orange cone out, i don't know....
i figure, if i left something out for that long, i have abandoned it. if someone can grab it and do something with it, by all means, do it. though i would have at least grabbed my lock back! then again, after having been vandalized i could totally see walking away from my property out of total disgust for humanity and never wanting to see it again...